Back to EveryPatent.com
United States Patent |
5,041,753
|
Clark
,   et al.
|
August 20, 1991
|
High torque magnetic angular positioning motor
Abstract
Axially elongated drive modules are interconnected at their opposite ends
angularly spaced supports in a polygonal arrangement on an inner ring to
establish tensile stress therein, while intermediate module centers are
spaced from an inner shaft by solenoid locks. Each module includes at
least two magnetostrictive rod elements held in axial alignment at their
adjacent ends by a coupling, through which the module is radially spaced
from the common axis. Drive coils electrically energized to generate
magnetic fields cause simultaneous elongation and contraction of the rod
elements to apply unidirectional torque to a rotor formed by either the
outer ring or the inner shaft.
Inventors:
|
Clark; Arthur E. (Adelphi, MD);
Teter; Joseph P. (Silver Spring, MD)
|
Assignee:
|
The United States of America as represented by the Secretary of the Navy (Washington, DC)
|
Appl. No.:
|
607345 |
Filed:
|
October 11, 1990 |
Current U.S. Class: |
310/328; 310/26; 318/118 |
Intern'l Class: |
H01L 041/08 |
Field of Search: |
310/26,317,323,328
318/118
|
References Cited
U.S. Patent Documents
4455501 | Jun., 1984 | Tojo et al. | 310/328.
|
4578607 | Mar., 1986 | Tojo et al. | 310/328.
|
4703464 | Oct., 1987 | Howarth et al. | 310/26.
|
4743792 | May., 1988 | Ueyama | 310/328.
|
Foreign Patent Documents |
1005585 | Apr., 1952 | FR | 310/26.
|
Primary Examiner: Stephan; Steven L.
Assistant Examiner: Rebsch; D. L.
Attorney, Agent or Firm: Walden; Kenneth E., Shuster; Jacob
Claims
What is claimed is:
1. In a device for converting electrical energy into mechanical energy,
including at least two active elements deformed by magnetic fields applied
thereto and coupling means interconnecting said elements for
unidirectional transmission of forces in response to simultaneous and
opposite deformation of the elements by said application of the magnetic
fields, an annular member, loading means connecting the annular member to
the elements for maintaining the elements under compressive stress
opposing said unidirectional transmission of forces, an anchoring member
and reaction means connecting the elements through the coupling means to
the anchoring member independently of the annular member for imparting
angular motion to one of said members in response to said unidirectional
transmission of forces.
2. The combination of claim 1 including motion control means operatively
connected to the anchoring member for limiting said angular motion
imparted to one of said members.
3. The combination of claim 1 wherein said active elements respectively
have adjacent longitudinal ends interconnected by the coupling means in
longitudinal alignment and opposite ends remote from the coupling means
connected by the loading means to the annular member at separate locations
thereon.
4. The combination of claim 3 wherein said annular member is made of a
material having greater stiffness than the elements to maintain said
elements under the compressive stress.
5. The combination of claim 3 wherein said loading means comprises rods
stiffer than the elements interconnected between the anchor member and the
annular member adjacent to the opposite remote ends of the elements.
6. The combination of claim 5 including motion control means operatively
connected to the anchoring member for limiting said angular motion
imparted to one of the members.
7. The combination of claim 6 wherein said motion control means includes
releasable lock means selectively connecting the coupling means and the
rods to the anchoring member and timing means operatively connected to the
releasable lock means for alternately effecting said selective connections
of the coupling means and the rods to the anchoring member.
8. The combination of claim 7 wherein said anchoring member is a stationary
shaft having angularly spaced portions engageable by the releasable lock
means.
9. The combination of claim 1 wherein said active elements respectively
have adjacent longitudinal ends interconnected by the coupling means in
longitudinal alignment.
10. In a device for converting electrical energy into mechanical energy,
including at least two active elements magnetostrictively deformed by
magnetic fields applied thereto and coupling means interconnecting said
elements for unidirectional transmission of forces in response to said
application of the magnetic fields, an annular member, loading means
directly connecting the annular member to the elements for maintaining the
elements under compressive stress, an anchoring member and reaction means
connecting the elements through the coupling means to the anchoring member
for imparting angular motion to one of said members in response to said
unidirectional transmission of forces, said active elements respectively
having adjacent longitudinal ends interconnected by the coupling means in
longitudinal alignment, said loading means including connector means for
fastening the respective opposite ends of the elements remote from the
coupling means to the annular member in fixed angular spaced relation and
compression rods interconnecting said connector means with the anchoring
member.
11. The combination of claim 10 further including releasable lock means
selectively connecting the coupling means and the connecting rods to the
anchoring member and timing means operatively connected to the releasable
lock means for alternately effecting said selective connections of the
coupling means and the connecting means to the anchoring member.
12. The combination of claim 11 wherein said anchoring member is a
stationary shaft having angularly spaced portions engageable by the
releasable lock means.
13. In a device for converting electrical energy into mechanical energy,
including at least two active elements magnetostrictively deformed by
magnetic fields applied thereto and coupling means interconnecting said
elements for unidirectional transmission of forces in response to said
application of the magnetic fields, an annular member, loading means
directly connecting the annular member to the elements for maintaining the
elements under compressive stress, an anchoring member and reaction means
connecting the elements through the coupling means to the anchoring member
for imparting angular motion to one of said members in response to said
unidirectional transmission of forces, said active elements respectively
having opposite ends and adjacent longitudinal ends interconnected by the
coupling means in longitudinal alignment and said compressive stress
establishing loading means including connector means for fastening the
respective opposite ends of the elements remote from the coupling means to
the annular member in fixed angular spaced relation and compression rods
interconnecting said connector means with the anchoring member.
14. In a device for converting electrical energy into mechanical energy,
including a rotor, an anchoring member, a plurality of drive modules,
loading means operatively connected to the rotor and the anchoring member
for establishing compressive stress in the modules between separate
locations on the rotor, coupling means interconnecting each of the modules
to the anchoring member independently of the rotor for transferring torque
to the rotor in response to deformations of the modules and power supply
means connected to each of the modules for inducing said deformations to
control the torque transferred to the rotor.
15. The combination of claim 14 wherein each of said modules includes at
least two magnetostrictive elements and field generating coils associated
therewith to which the power supply means is connected, said elements
having opposite remote ends fastened by the loading means to the rotor at
said separate locations in relative fixed spaced relation.
16. In a device for converting electrical energy into mechanical energy,
including a rotor, at least one drive module, a power source, field
generating means connected to said source for inducing deformations of
opposite character within the module between fixedly spaced locations on
the rotor, loading means connected to the module at said fixedly spaced
locations on the rotor for establishing compressive stress in the module
and reaction means connected to the module independently of the rotor for
enabling unidirectional transmission of driving torque to the rotor in
response to said deformations.
17. The combination of claim 16 wherein said module includes at least one
pair of force transmitting subassemblies and coupling means for
interconnecting said subassemblies, said deformations of opposite
character being simultaneous elongation and contraction of the respective
subassemblies between the reaction means and the loading means to induce
angular motion of the rotor.
18. The combination of claim 17 wherein each of said force transmitting
subassemblies includes at least two active elements and flux conducting
connectors interconnecting said elements in parallel between the reaction
means and angularly spaced locations on the rotor.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to the conversion of electrical power into
mechanical power in the form of high-torque rotary motion, and more
particularly in the use of magnetostriction to accomplish such purpose.
Magnetostriction motors are generally well known in the art and involve the
use of an active magnetostrictive body such as an elongated rod which
undergoes dimensional change when magnetized by a field generated by
electrical energization of a surrounding drive coil, as disclosed for
example in U.S. Pat. No. 2,105,479 to Hayes. The use of a plurality of
such magnetostrictive rods interconnected in various arrangements are also
known in the art, as disclosed for example in U.S. Pat. Nos. 3,439,199 and
3,634,742 to Bergstrand et al and Edson, respectively.
The foregoing magnetostrictive motors transform electrical power directly
into mechanical linear motion. Various gearing arrangements or the like
would therefore be required in order to convert such linear motion into
rotary motion or angular displacement. In conventional electrodynamic
motors, a rotary motion output at high torque is obtained by use of
unwieldly and costly reduction gear boxes with an accompanying decrease in
rotational speed. Such gear boxes are usually associated with undesirable
backlash and friction, creating problems in achieving angular positioning
accuracy and performance maintenance.
It is therefore an important object of the present invention to
magnetostrictively transform electrical power into rotary motion at a high
torque without any gear boxes and the aforementioned problems associated
therewith.
Another object of the invention in accordance with the foregoing object is
to more directly and efficiently convert electrical power into rotary
motion at high torque levels by utilization of magnetostrictive materials.
SUMMARY OF THE INVENTION
In accordance with the present invention, a plurality of magnetostrictive
modules are respectively connected in radially spaced relation to an
anchor member to define a common rotational axis. The modules are
connected at opposite longitudinal ends thereof at angular spaced location
on an annular ring to form a polygonal arrangement of the modules of a
rotary unit. Each module includes at least two magnetostrictive rod
elements held in axial alignment with each other at adjacent ends by a
coupling through which the rod elements are anchored relative to the
anchor member aforementioned. Field generating drive coils are mounted on
each of the two rod elements of each module and are electrically energized
during drive cycles to simultaneously cause axial elongation of one rod
element and axial contraction of the other rod element in each module.
Such simultaneous and opposite magnetostrictive deformation of the rod
elements when anchored at their adjacent ends transmits forces in one
linear direction through its module which is fastened in chordal relation
directly to the annular ring aforementioned in order to establish a
compressive stress in the module. A high rotational torque is thereby
produced during each drive cycle as a function of the ratio of the axial
length of the rod elements in each module and its radial spacing from the
common rotational axis. Either the anchor member or the annular ring may
act as the rotor while the other is held stationary as a reaction frame.
High torque is obtained by means of the foregoing arrangement as a result
of high atomic forces of magnetostriction in the rod elements of each
drive module. It is accordingly desirable to use materials with large
magnetostriction exceeding 1000 ppm, for example, such as the rare
earth-iron compound Terfenol-D referred to in our copending application,
Ser. No. 07/607,350, filed Oct. 11, 1990.
BRIEF DESCRIPTION OF DRAWING FIGURE
Other objects, advantages and novel features of the invention will become
apparent from the following detailed description of the invention when
considered in conjunction with the accompanying drawing wherein:
FIG. 1 is a transverse section view of a rotary unit of a magnetostrictive
motor constructed in accordance with one embodiment of the invention.
FIG. 2 is a side section view taken substantially through a plane indicated
by section line 2--2 in FIG. 1.
FIG. 3 is an enlarged partial section view taken substantially through a
plane indicated by section line 3--3 in FIG. 2.
FIG. 4 is a simplified block diagram of the electrical power system
associated with the rotary unit of the motor depicted in FIGS. 1-3.
FIG. 5 is a partial transverse section view of a magnetostrictive rotary
motor unit in accordance with another embodiment of the invention.
FIG. 6 is a partial side section view of a plurality of rotary motor units
in accordance with yet another embodiment of the invention.
FIG. 7 is a partial section view taken substantially through a plane
indicated by section line 7--7 in FIG. 6.
FIG. 8 is an enlarged partial transverse section view showing another
embodiment of the drive modules in the motor depicted in FIG. 3.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawing in detail, FIGS. 1-3 illustrate a rotary unit
of a magnetostriction motor generally referred to by reference numeral 10
constructed in accordance with one embodiment of the invention. In this
embodiment of the invention, a mechanical power output shaft 12 as shown
in FIG. 2 extends from an annular ring type rotor 14 of circular
crosssection. The annular ring 14 is journalled on a stationary shaft 16
acting as a reaction anchor frame in axial alignment with rotor shaft 12.
A rotor-enclosing housing 18 may be connected to anchor shaft 16 as shown.
Mounted within the rotor ring 14 about the anchor shaft 16 are a plurality
of magnetostrictive drive modules of the expand contract type,
respectively referred to by reference numeral 20, arranged in chordal
relation to the rotor ring 14 internally thereof to form an equilateral
polygon therein as shown in FIG. 1. The modules 20 are rigidly fastened to
each other at opposite longitudinal ends thereof and to angularly spaced
portions of the annular rotor for module loading purposes by suitable
connectors 22. As more clearly seen in FIG. 1, four of such modules 20 are
utilized in the illustrated embodiment, by way of example, to form a
square in chordal relation to the rotor about its rotational axis which is
coincident with the geometrical axis of the anchor shaft 16.
As also shown in FIG. 1, compression rods 24 extend inwardly from each of
the module loading connectors 22 in radial relation toward the anchor
reaction shaft 16. Electrically operated lock devices 26 are associated
with the compression rods 24 while electrically operated lock devices 28
are associated with the modules 20 to selectively control alternate
connection of compression rods and modules to the anchor shaft as will be
explained in detail hereinafter.
Referring now to FIG. 3 in particular, each of the modules 20 includes at
least one pair of axially aligned magnetostrictively active elements 30
having adjacent ends interconnected by a coupling 32 from which one of the
lock devices 28 extends radially inwardly toward the anchor shaft 16. The
opposite remote ends of the magnetostrictive elements 30 are fastened to
the rotor ring 14 by two of the loading connectors 22. Magnetic field
applying coils 34 and 35 are respectively mounted about the two elements
30 of each module as shown to generate properly phased magnetic fields
with respect to the common longitudinal axis of the elements 30 in each
module.
Each of the modules 20 is selectively connected to the anchor shaft 16
through its coupling 32 by energization of electromagnetic coil 36 in its
lock device 28 to project a solenoid plunger 38 with a friction pad 40
thereon into engagement with the anchor shaft 16, as more clearly seen in
FIG. 2, in order to enable application of torque to the rotor. Similarly,
each rotor lock device 26 is energized through its electromagnetic coil 42
as shown in FIG. 3 to project its solenoid plunger 44 with a friction pad
thereon into engagement with the anchor shaft 16 as shown in FIG. 1, in
order to fixedly anchor the rotor in its static condition through the
compression rods 24. Other lock engaging devices could of course be
utiized to perform the same function.
As diagrammed in FIG. 4, a suitable source of electrical power 48 is
connected to a coil driver power supply 50 through which the
aforementioned magnetic fields are simultaneously established in each of
the modules 20. Accordingly, one of the two force transmitting
subassemblies respectively formed by the elements 30 and their drive coils
in each of the modules is magnetostrictively deformed to cause
longitudinal elongation or expansion thereof while, at the same time, the
element 30 of the other force transmitting subassembly is
magnetostrictively contracted in the same longitudinal direction. Such
simultaneous and opposite deformations of the two subassemblies in each
module 20 with adjacent ends thereof anchored to the shaft 16 exert
simultaneous axial forces in the same direction from the remote ends
thereof to the rotor ring 14 at the angularly spaced chordal locations of
the connectors 22. Accordingly, an increased rotational torque is applied
by each module to the rotor by virtue of the opposite nature of the
simultaneous deformations of such modules relative to end adjacent end
portions of the force transmitting subassemblies, respectively formed by
the active elements 30 and the coils 34 and 35. The rotor will thus
undergo unidirectional angular displacement by a limited amount (.theta.)
during an operational cycle while the modules 20 are anchored to shaft 16
by energization of their lock devices 28. At the end of such drive cycle,
the rotor is locked to anchor shaft 16 by the rotor lock devices 26 to
enable application of longitudinal compressive stress to the modules
through the compression rods 24 as the modules are released from the
anchor shaft 16 by deenergization of the lock devices 28. The elements 30
therefore return to their static condition under the longitudinal
compressive stress before the next drive cycle is repeated with release of
the rotor by deenergization of the lock devices 26. The power source 48 as
diagrammed in FIG. 4 is accordingly connected to a timing control 50
through which the module lock devices 28 and rotor lock devices 26 are
alternatively energized in proper timed relation to each other to enable
optimum intermittent application of unidirectional torque to the rotor by
energization of the module coils 34 and 35 under control of the coil
driver supply 50.
In the embodiment described with respect to FIGS. 1-4, the compression rods
24 are mechanically stiffer than the active elements 30 of the modules in
order to establish the necessary longitudinal compressive stress therein
between drive cycles. Such compression rods may be eliminated together
with their lock devices 26 by selection of a material for the rotor which
is stiffer than the active elements of the magnetostrictive modules so as
to be relatively nondeformable between the locations of connectors 22 and
act as an outer compression ring for the modules. FIG. 5 shows such an
embodiment wherein a rotary unit includes magnetostrictive modules 20'
with their remote longitudinal ends connected to an oval shaped rotor 14'
by connectors 22'. Bracing rods 54 extend between connectors 22' in
chordal relation to the rotor 14' which acts an outer compression element
for the modules. The modules 20' are furthermore permanently anchored by
their intermediate couplings 32' to a common anchor shaft 16'.
In each of the foregoing embodiments of the invention, wherein the rotor
forms a radially outer ring rotated relative to an inner reaction anchor
shaft, the angular displacement (.theta.) of the rotor when the module
coils are energized is given by the formula .theta.=.lambda.L/R, where
(.lambda.) is the magnetostriction of the material of the active elements
30 as a function of the magnetic fields or field generating current. The
dimensions (L) and (R) respectively represent the length of the module
elements 30 and the radial spacing of the modules from their common
rotational axis as denoted in FIGS. 1 and 5. It will be apparent from the
foregoing formula that the angular displacement (.theta.) may be increased
by increasing the ratio L/R as a design option by selection of an oval
shaped rotor as shown in FIG. 5 rather than a circular shaped rotor shown
in FIG. 1. Angular displacement may also be increased by different
stacking arrangements of individual rotary units as illustrated in FIGS. 6
and 7, by way of example. The individual rotary units shown in FIG. 6 have
their outer rings and inner anchoring shafts functionally interchanged by
interconnecting the outer annular ring 14" of one unit with rotatable
rotor shaft 14'" of the next unit, with which an annular ring 16'" is
associated acting as a frame reaction member.
FIG. 8 illustrates a modified form of module wherein each force
transmitting element 30 and associated coil 34 or 35 is replaced by a
magnetostrictive subassembly formed by two parallel active elements 56 and
58 interconnected at opposite ends by flux conducting connectors 60 and
62. The elements 56 and 58 are respectively surrounded by field generating
coils 34a and 34b of the same polarity. Two of such subassemblies which
are identical are interconnected at adjacent ends in longitudinal
alignment and anchored threat by coupling 32". The remote ends of the
subassemblies are fastened to the rotor 14" by connectors 22".
Numerous other modifications and variations of the present invention are
possible in light of the foregoing teachings. It is therefore to be
understood that within the scope of the appended claims the invention may
be practiced otherwise than as specifically described.
Top